Inconsistency With Layer Priority

I am seeing something strange with layer priority settings that I have applied. I spent some time reading up on this and my layer priority settings are not performing as I'd hoped.

We have a package called Lync deployed which has Silverlight v4 bundled with it (by mistake) which means that now we wish to deploy Silverlight v5 without having to change the Lync layer. The Lync layer has been deployed with the default layer priortisation rules (Normal: 85.5, HKCR: 65.5)

I packaged Silverlight v5 in its own layer and set the HKCR priority to 65.4 (svscmd silverlightv5 -t HKCR -L 65.4) which I expect this means that it should take precedence over the Silverlight v4 in the Lync layer.

Howver in our test environment the results are inconsistent, sometimes the Microsoft Silverlight page will say v4 is installed, sometimes it will say v5 is installed.

If I set both Normal and HKCR to higher, this breaks the virtualisation so I assume I can only set the prioritisation on one or the other?

Both layers are set to activate on startup, using SWV Admin v6.1 SP8, Symantec Management Agent 7.1.15400.8400

Issue is on both Windows7 x86 & x64

I would appreciate any pointers on this, maybe I don't have this quite right? Has anyone else out there used layer priortisation rules with success?